Advanced Research Design, Analysis, and ApplicationsDr. George H. Olson, Instructor

Variables in Research

Concepts and constructsMany (actually most) variables cannot be viewed directly, are not manifest. Latent variables are constructs or concepts. Abstractions to simplify thinking and aid communication. Concepts and constructs differ in degree of abstraction.

ConceptsRepresent common characteristics of phenomena. Abstractions formed by generalizing form particulars. Examples:weight mass attention audio acuity sports car cocktail dress

ConstructsDeliberate, conscientious inventions for specific scientific purposes. Examples:Reading readiness (included visual perception, sight-sound discrimination, audio acuity, and left-to-right orientation.Creativity Learning Permissiveness Intelligence Motivation Leadership

VariablesAny event, category, behavior, or attribute that can:take on different values, and can be measured.

Examples:age test score class size type of instruction group assignment size of print achievement motivation creativity

Values of VariablesMeasurements (numbers) assigned to variables. Examples:VARIABLE Sex Religion Math ach. VALUE 0 if male; 1 if female 1 if Catholic; 2 if Protestant; 3 if Jewish; 4 if other Score on some math test

Different Types of VariablesIndependent variables. Dependent variables. Attribute variables. Extraneous variables. Confounding variables. Intervening variables.

Independent VariablesTrue independent variables:Experimental. Manipulated. Controlled.

Quasi independent variables:Naturally occurring. Organic or biological. Quasi-experimental.

Dependent VariablesEffects. Outcomes. Measured variables. Dependent variables are functions of independent variables.dv ! f iv ach ! f hrs.of study

Attribute VariablesCharacteristics or Attributes. May effect the dependent variables. Examples:age sex race experience attitude advantagement

Extraneous VariablesNuisance or controlled variables. Irrelevant to the focus of the study. Can affect interpretation of results. Examples:time of day side of building age of school building sequence of events sex of investigator current events

Confounding VariablesExtraneous variables whose effects on the dependent variables cannot be distinguished from those of the independent variable(s). Usually occurs when an extraneous variables is correlated with one or more independent variables.

Intervening VariablesBlack box variables. Invented to account for internal, unobservable psychological processes that intervene between independent and dependent variables. E.g. learning intervenes between teaching and achievement: ind var p int var p dep var

Continuous VariablesNumerical data in research can be classified as either continuous or discrete. Variables that can take on any of a continuously ordered set of values within some specified range. Examplesage experience achievement dogmatism motivation intelligence

Discrete VariablesVariables whose values can only be whole numbers. Characterized by gaps in the measurement scale. Typically represent counts of things.number of children size of family school enrollment number of books

Continuous or Discrete?The distinguishing characteristic between continuous and discrete variables. concerns the continuity of the underlying attributes or traits being measured--not the measurements themselves.Variables that often appear discrete are actually assumed to be continuous. For example scores on tests are usually considered to be continuous.

Continuous or Discrete: Can you tell?How would you classify the following variables? Continuous or discrete?Grade Level Occupation College classification Time on task

Actually it depends upon how these variables are defined.What is the underlying characteristic or trait? Is it continuous or naturally discrete?

Defining Variables use in ResearchTwo ways of defining variables (and concepts or constructs). Constructive definitions. Operational definitions.

Constructive DefinitionsDictionary-type definitions. Define a variable in terms of other variables, concepts, or constructs:anxiety: apprehension or vague fear. intelligence: mental acuity, the ability to think abstractly. achievement: successful completion or accomplishment.

Constructive DefinitionsTo be scientifically useful, all constructs must possess constitutive meaning. Constructive definitions open the door to ambiguity. Constructive definitions are insufficient for scientific research. For example, define creativity in such a way that the meaning would be clear to others.

Operational DefinitionsSpecify the activities or operations that are necessary for measuring, categorizing, or manipulation of the variable. Facilitate replicability. Two types of operational definitions:Experimental operational definitions. Measurement-based operational definitions.

Experimental Operational DefinitionsProvide detailed account of how the variable in manipulated. Typically used for defining independent variables. Example:Reinforcement: defined by giving detailed instructions on how children are to be reinforced (rewarded) or not reinforced.

Experimental Operational DefinitionsAnother example:In one study frustration was operationally defined as preventing children from accessing highly attractive toys. The toys, while clearly visible to the children, were placed behind a wire partition. The attractiveness of the toys was defined as those toys chooses most often by children.

Operational Definitions Based on MeasurementDescribe how a variable is measured. Gives the rules for assigning numbers to values of the variable. Example:Achievement can be defined as the score on a standard achievement test, a score on a teacher-made test, or a grade on a report card.

Operational Definitions Based on MeasurementOther examples:Consensus might be defined as the similarity of several individuals ratings of the quality of ten pieces of camping equipment. Rude classroom behavior could be defined as the number of times a student talks out loud when not called upon. Writing productivity was defined, in one study, as the number of words produced in a writing task

Examples Operational Definitions of ConstructsTest anxiety (1): Induce levels of anxiety by varying the conditions under which a test is given: practice (low), quiz worth minimal points (moderate), high stakes (high). Test anxiety (2): A measure of test anxiety obtained from the revised and shortened version of the Test Anxiety Questionnaire.

Examples Operational Definitions of ConstructsAchievement (1): Achievement was measured as the grade-point-average, on a scale from 0 to 4, obtained from grades in core courses (math, science, social studies, and language arts). Achievement (2): The composite score on the CTBS comprised our measure of achievement.

Examples Operational Definitions of ConstructsTeacher-principal agreement: The correlation between the average teacher ratings on the importance of a specific list of instructional goals and the principal s rating of the importance of the same list of goals. Institutional quality: The average academic ability of entering students.

Examples Operational Definitions of ConstructsHonesty: A child was considered dishonest if the inside of his test booklet showed: (a) that he had changed his answer by drawing a circle around his wrong response and had made an X for the correct response; (b) that he had erased the wrong response and marked the correct one; or (c) that he marked the correct response when checking his paper but his work on the in the booklet did not agree with his answer.